The Da Vinci Code

Langdon believes the cryptex is the Priory’s legendary keystone, said to lie “beneath the sign of the Rose.” He asks Sophie if Saunière ever mentioned a clef de voûte—the French phrase for “keystone.” The word originally refers to the central stone which holds an archway together. Rumor has it the Priory’s keystone is encoded with a map to the Grail. Though Langdon is primarily interested in Grail symbology, he has heard of historians searching for the keystone in the archways of French churches, many of which feature architectural roses. Certain Saunière made the cryptex, Sophie argues that it can’t be an ancient keystone. But Langdon has heard the Priory only created the keystone in recent decades, to increase security.

Langdon explains that the Priory passed on the Holy Grail’s location verbally to each rising sénéchal, never writing this secret down. With the advent of electronic eavesdropping, they allegedly stopped speaking the location, instead subjecting sénéchaux to a test of worthiness. If a Priory member can open the keystone, they prove themselves worthy of the knowledge it contains. Sophie confesses her suspicions that Saunière was the Priory’s Grand Master, based on what she witnessed 10 years ago. Langdon thinks this makes sense—Priory Grand Masters were often artists and cultural influencers. He wonders again why Saunière wanted to meet with him. The truck stops. Vernet opens the cargo hold and points a pistol at them.